Windows including glass substrates with solar control coatings provided thereon are known in the art. Such windows may be used in the context of architectural windows, insulating glass (IG) window units, automotive windows such as windshields, and/or the like.
Related U.S. patent application Ser. No. 10/400,080 discloses at least a coated article having the following layer stack where the layers are listed in order from the glass substrate outwardly:
TABLE 1(Example Materials/Thicknesses; 10/400,080)LayerThickness (Å)TiOx 40 ÅSixNy113 ÅZnOx100 ÅAg 95 ÅNiCrOx 26 ÅSnO2483 ÅSixNy113 ÅZnOx100 ÅAg131 ÅNiCrOx 26 ÅSnO2100 ÅSi3N4226 Å
While the aforesaid coated article of Ser. No. 10/400,080 is excellent in most respects, there is room for improvement.
In particular, the aforesaid coating when used in applications such as laminated windshields may be problematic in the following areas. First, it tends to sometimes be too red/purple with respect to reflective color. It would be desirable if more neutral reflective color could be achieved. Second, durability is sometimes lacking. For example, when exposed to conventional brush testing for durability following heat treatment (HT), delamination often occurs.
It would be desirable if one or both of the aforesaid two problems could be addressed and/or solved.
Turning to another separate and distinct issue, it is known that if one wants to improve a coating's solar performance (e.g., infrared reflection), the thickness of the silver layer(s) can be increased in order to decrease the coating's sheet resistance. Thus, if one wants to improve a coating's solar performance by increasing its ability to reflect infrared (IR) rays or the like, one typically would increase the thickness of the IR reflecting silver layer(s). Unfortunately, increasing the thickness of the silver layer(s) causes visible transmission (TY or Tvis) to drop. Accordingly, in the past, when one sought to improve the solar performance of a coating in such a manner, it was at the expense of visible transmission. In other words, when solar performance was improved, visible transmission was sacrificed and decreased. Stated another way, it has been difficult to increase the ratio of visible transmission to sheet resistance (i.e., Tvis/Rs), especially if heat treatability and/or durability are to be provided. This is why many coatings that block (reflect and/or absorb) much IR radiation have a rather low visible transmission.
An excellent way to characterize a coated article's ability to both allow high visible transmission and achieve good solar performance (e.g., IR reflection and/or absorption) is the coating's Tvis/Rs ratio. The higher the Tvis/Rs ratio, the better the combination of the coating's ability to both provide high visible transmission and achieve good solar performance.
Certain heat treatable coatings cannot achieve very high Tvis/Rs ratios, thereby illustrating that their combined characteristic of visible transmission relative to sheet resistance (and solar performance) may be improved. In the past, it has been theoretically possible to increase the Tvis/Rs ratio, but not in a commercially acceptable manner. As an example, Example 2 of U.S. Pat. No. 4,786,783 could not survive heat treatment (e.g., heat bending, tempering, and/or heat strengthening) in a commercially acceptable manner. If Example 2 of the '783 patent was heat treated, the sheet resistance would effectively disappear because the silver layer(s) would heavily oxidize and be essentially destroyed, thereby leading to unacceptable optical properties such as massive (very high) haze, very large ΔE* values, and unacceptable coloration. For example, because Example 2 of the '783 patent does not use sufficient layer(s) to protect the silver during HT, the coated article would have very high ΔE* values (glass side reflective and transmissive) due to heat treatment; ΔE* over 10.0 and likely approaching 20.0 or more (for a detailed discussion on the meaning of ΔE*, see U.S. Pat. Nos. 6,495,263 and/or 6,475,626, both of which are hereby incorporated herein by reference).
In view of the above, it may be desirable to improve the aforesaid coating of Ser. No. 10/400,080 or other coatings at least with respect to durability and/or reflective coloration. Moreover, in certain example instances, it may be desirable to provide a coating with good visible transmission without sacrificing solar performance and/or good solar performance without sacrificing visible transmission. With respect to this latter point, it may in certain example non-limiting situations be desirable for the Tvis/Rs ratio to be high in a coating that may be heat treated in a commercially acceptable manner.